2G Question about rotor size and caliper position

[PieEyedPiper]

Check out this thread for the details: http://www.dsmtuners.com/forums/showthread.php?t=197866

I'm trying to find out if anyone can answer my question, if so please post in the thread above.

Also, if these rotors are 303mm (read: bigger than ours) and we use the stock mounts with the XG caliper, or even our own calipers (despite any required modding), would that not defeat the purpose of larger rotors?

If I understand correctly, you have greater braking power with a larger rotor due to leverage, right?

But what happens if our caliper is grabbing at the same height on the larger rotor as it would on the stock ones? would it effectively give us the same breaking ability since its not using the enhanced diameter of the new rotors?

maybe I'm over-analyzing.

 

[SlowSpyder]

Larger rotors and especially thicker rotors have greater thermal capacity

 

[PieEyedPiper]

granted, but aren't we still missing out on the added leverage? - which would have a greater effect on stopping power?

 

[wret]

Yes, greater diameter = greater leverage = more braking power.

That story you linked to seems a little over-simplified. The Tiburon rotors may fit but there's more custom work involved than he told us about. Unless you can do the customization yourself, you may not save anything over a bolt-on kit.

 

[Todd TCE]

Leave width and thermal capacity out of it. That has nothing to do with 'power' which really is torque in the proper term.

Larger rotor will increase torque. BUT....that's only part of the equation.

You'd really need to know the piston area of both calipers (old and new) to speak total torque or 'more power'.

If the new caliper has less piston area, even on a larger rotor (assuming same pad compounds in both) you may actually lose torque. And just because you put on the larger rotor that in itself won't make the car stop quicker. More diameter simply means the pistons don't have to bite as hard (i.e. lower line pressure required) to do the same job. They are not really making more 'power' they are simply changing the way it's done.

On the final hand, if the rotors are larger and the total piston area is greater then the whole combo can produce more total torque then the previous set up. At far less line pressure. Sounds good huh? But it comes at a price; poor pedal feel and loss of rear brake bias.

 

[PieEyedPiper]

wret, i think you're crossing the two upgrades listed in that thread. There is no modding other than slight grinding to make it all fit... at least as far as I could tell.

I've taken into account all the info presented in both these threads and I've concluded that "upgrade" isnt much of an upgrade due to the "lack of torque" gained. Without that extra leverage, there cant be much greater braking power other than that from larger heat capacity etc. Also, as pointed out, piston surface area would be a key element.

unless that caliper from the XG is grabbing the rotor higher up than our stock calipers would, this isn't much of an upgrade at all.

Can anyone verify this?

 

[Todd TCE]

Give me the exact specifics and I can spit out the bias numbers completely.

Rotor size of each.
Piston size (s) of each.
We'll assume the same pads.


PADS: yes if one of the pads is taller and skinnier than the other you have shifted the Effective Radius of the pad. That will change the torque value. Most street pads tend to be about 2.25" wide so they are not as stout as the narrower 1.75 of aftermarket caliper pads.